Turbine or compressor blade

ABSTRACT

A blade for a turbine or a compressor, at least partially made of fiber-reinforced plastic, in particular carbon fiber reinforced plastic, being particularly durable under operating conditions is provided. The blade includes a blade body and a blade root. The blade body is substantially made of a folded fabric web made of fiber reinforced plastic, wherein a retaining loop is formed in the area of the fold, and wherein a blade surface is formed in the area of the fold, and wherein a blade surface is formed from the overlapping web ends. The blade root includes a longitudinal beam and at least two holders for anchoring the blade in a corresponding groove of a rotor, the holders being preferably each fixedly connected to the beam at both ends. The blade body is suspended on the beam by means of the retaining loop.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2010/067581, filed Nov. 16, 2010 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 09014381.9 EP filed Nov. 17, 2009. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a blade of a turbine or of a compressor.

BACKGROUND OF INVENTION

A blade of a turbomachine on the one hand normally comprises an aerodynamically curved blade airfoil and, on the other hand, normally comprises a blade root which serves for anchoring the blade in a corresponding groove of a rotor. The rotor equipped with blades is referred to as rotor assembly in the following text.

As a comparatively new type of material for producing blades, even carbon-fiber reinforced plastic (CFK) is currently taken into consideration. The production from CFK advantageously gives rise to a lower weight of the blade, for example. CFK, however, disadvantageously has comparatively low stability in relation to pressure loading. Such pressure stresses develop on a blade, for example in the region of the blade root inside the groove, as a result of the effect of a rotation-induced centrifugal force.

To this end, a rotor blade—produced from a fiber composite material—of a turbomachine is known from U.S. Pat. No. 4,037,990, for example. The rotor blade consists of a multiplicity of fiber-like layers which on their root-side end form a common loop. In this case, two of these loops are provided for forming the blade root. For fastening the rotor blade in a rotor disk, provision is made for a longitudinally slotted bolt, the bolt element of which extends through the respective loop. The bolt head and a threaded nut, which can be screwed on the bolt end, fixedly clamp the blade in an axial groove of the rotor. During operation of the turbomachine, the fiber-like layers are pressed against the load-bearing flanks of the retaining groove on account of centrifugal force action. On account of the pressure stresses which occur in the layers in the process, the rotor blade can be retained only to a limited extent, however. Furthermore, a rotor blade for gas turbines, which on the root side has a cylindrical, rigid core, around which are laid a multiplicity of woven layers produced from filaments in a loop-like manner, is known from U.S. Pat. No. 2,929,755. The blade airfoil is also formed from the layers. For fastening the rotor blade in a retaining groove, provision is made on the core for metal plates which bear against the flanks of the retaining groove. A filling material, consisting of plastic, is provided between the two metal plates in order to fill out the space between the outermost layer and the retaining groove contour.

SUMMARY OF INVENTION

The invention is based on the object of disclosing a blade, which is produced at least partially from fiber-reinforced plastic, especially CFK, for a turbine or a compressor, which blade is particularly resistant, i.e. durable. It is also an object of the invention to disclose a rotor assembly, which is particularly durable under operating conditions, having blades which are produced essentially from fiber-reinforced plastic.

In respect to the blade, this object is achieved according to the invention by means of the features of the claims. According to this, in addition to an aerodynamically curved blade airfoil the blade comprises a blade root with an elongated or pin-like carrier which in a preferred embodiment is produced from metal. The blade root also comprises at least two holders, wherein these preferably plate-like holders are connected to the carrier in a positionally fixed manner, at least in its radial direction. Each holder is designed for anchoring the blade in a corresponding inverted T-shaped or firtree-shaped groove of a rotor and can bear against its sidewalls.

The blade airfoil is produced essentially from layered fabric webs consisting of fiber-reinforced plastic, especially CFK, which is guided (essentially between the holders) around the carrier. In this case, the two web ends which project beyond the carrier in each case are interconnected in flat manner for forming a blade surface. The part of the blade airfoil which is guided around the carrier foams a retaining loop for attachment of the blade airfoil on the carrier. In respect to production engineering, it is preferably provided in this case to first produce the laminated fabric for the forming of the blade airfoil (that is to say of the blade surface and the retaining loop), and to then fit the thus-produced blade airfoil onto the carrier. Alternatively to this, the laminated fabric can naturally also be attached around the carrier for the forming and profiling of the blade airfoil adjoining it.

In the normal installed situation of the blade, this lies with its blade root—i.e. with the retaining loop of the blade airfoil together with the carrier arranged therein—in the groove of the rotor, whereas its blade airfoil, with regard to the rotor, essentially projects radially from the groove.

Since the blade airfoil is attached on the carrier by means of the retaining loop, rotation-induced centrifugal forces which act upon the blade are absorbed in the main via the carrier. A direct transfer of force between the blade airfoil and the rotor groove does not take place, or takes place only to a comparatively small degree. Therefore, the blade airfoil or its laminated fabric for the most part is under tensile stress.

Since fiber-reinforced plastic is many times more resistant to tensile loads than to pressure loads or shear loads, the blade, and particularly its fastening section in the four of the blade root, is therefore particularly resistant and durable in respect to operating conditions.

The use of fiber-reinforced plastic, especially CFK, for producing the blade airfoil advantageously opens up the possibility in general of constructing an aerodynamically particularly favorable blade airfoil. This therefore contributes to a reduced energy input, which in turn is advantageously accompanied by a reduced development of CO₂. On account of the lower weight of the fiber-reinforced plastic, the blade airfoils of such blades can be even larger than blade airfoils of metal blades, with a blade root of the same size. This also enables an increase of the mass flow.

The individual holders of the blade root are interconnected by means of at least one flank section for stabilizing the blade root, wherein this flank section is oriented essentially parallel to the carrier.

Provision is preferably made in this case for two flank sections which are attached in each case on the two lateral edges of each of the holders, with which the respective holder projects over the blade airfoil. Accordingly, the two flank sections lie preferably diametrically opposite with regard to the carrier. In particular, the attachment of the flank sections is again carried out in this case in such a way that these do not come into contact with the laminated fabric web, at least in the region in which the holders project over the blade airfoil. As a result of this, the unwanted pressure stresses in the laminated fabric webs are reliably avoided. In the case of trapezoidal holders, the flank sections are preferably fastened to the two sides of the trapezoid so that the force flux takes place entirely via the flank sections. This reduces the end-side loading of the retaining groove enormously and so evens out the loading in the rotor disk on account of the contact surfaces which are significantly enlarged by the flank sections. Consequently, the steeples which are arranged between two adjacent retaining grooves can be made smaller, as a result of which a compact, space-saving arrangement of retaining grooves in the rotor is possible.

In an especially preferred embodiment of the invention, each of the holders, in the region of the carrier, projects over the blade airfoil on both sides, at least in the main at right angles to the longitudinal extent thereof. In other words, in such configurations the holders, in the region of the attachment of the blade airfoil, project over the laminated fabric web on both sides so that the laminated fabric, at least in the region there, does not come into contact with the corresponding lateral surfaces of the groove (of the groove flanks). Consequently, the blade, under centrifugal force, bears principally against the groove flanks only via the holders and not via the laminated fabric, so that only the holders experience pressure stresses. This avoids pressure stresses in the root-side laminated fabric regions which could occur on account of centrifugal force action if the root-side laminated fabric were to come into contact with the groove flanks.

Each of the holders expediently also projects over the blade airfoil on the normally radially inner side (facing away from the blade surface) of the blade so that the laminated fabric web is also attached in the groove base of the rotor groove in a contact-free manner.

In a further embodiment of the invention, the blade root comprises two holders, which are attached particularly at the ends of the carrier, and also at least a third holder, wherein this is positionally fixed on the carrier, in the longitudinal direction of said carrier, at a distance from each of the two holders which are attached at the ends. These additionally provided holders are preferably distributed evenly over the length of the carrier. In this embodiment, the blade airfoil is expediently produced from a plurality of laminated fabric webs which are attached on the carrier in each case between two holders and therefore positionally fix the middle holders in the longitudinal direction of the carrier. In principle, the two fastening positions of the holders on the elongated carrier are selected in dependence upon the center of gravity of the blade so that a fastening position of the holders which is not arranged at the ends, but in the region of the carrier ends, may also be advisable.

Each of the holders is preferably provided with a penetration which corresponds to the cross section of the carrier and through which the carrier is inserted in an essentially accurately fitting manner in each case. As an option, the carrier is welded to the holders.

The flank sections are expediently connected in each case to the holders in a form-fitting or materially bonding manner, preferably plugged in or welded.

The carrier is preferably of a round shape or essentially of a triangular shape in cross section. In the case of a triangular shape, an isosceles triangle, especially with rounded edges, is preferred, wherein the edge which is included by the two sides in particular approximately faces the blade surface of the blade airfoil.

The carrier is preferably provided with a sliding layer, especially with a layer consisting of polytetrafluoroethylene, on its surface. As a result of this, if necessary, the innermost laminated fabric web can slide relative to the carrier.

The laminated fabric, in an advantageous development of the invention, is of an essentially unidirectional form, wherein it has a main fiber direction which is oriented essentially along an operation-induced centrifugal force direction. The blade airfoil is especially stable in relation to the occurrent tensile forces as a result of this. The laminated fabric is additionally or alternatively reinforced in the region of the blade root or in the region of the carrier by means of a three-dimensional interwoven structure of the fibers.

The blade airfoil, at least in the region of its blade surface, is expediently provided with an erosion-proof coating, especially consisting of a particle composite or of a metal foil coated with a hard substance, on its surface. This coating advantageously also improves the resistance of the blade to the ingress of water.

With regard to the rotor assembly, the aforesaid object is achieved according to the invention by means of the features of claim 12. According to this, the rotor assembly comprises a rotor, into which at least one groove is introduced, and at least one of the previously described blades according to the invention. The blade lies by its blade root in the groove in a positionally fixed manner.

As a result of the comparatively low weight of the blades which are produced essentially from fiber-reinforced plastic, each of the provided grooves in the rotor is of an advantageously comparatively small design. Moreover, the entire rotor assembly is advantageously particularly light. Naturally, the blade root can also be of a disproportionately large design in relation to the blade airfoil if the blade according to the invention in an operationally stressed turbomachine is to replace a blade produced purely from metal or high-grade steel.

The groove and the holders are preferably matched to each other in such a way that the holders are supported in each case on the lateral surfaces of the groove. In particular, the holders essentially fill out the groove cross section in an expedient construction.

Both the holders and the groove are preferably of an essentially trapezoidal design (“dovetail groove”) in cross section. Other cross-sectional shapes, e.g. a “firtree shape” or half-round shapes, are also possible for holders and groove cross-sectional contours.

In an expedient development of the invention, the holders of the blade are formed congruent to each other, wherein the groove has a uniform width and shape over its length.

In a preferred development of the rotor assembly, this comprises a multiplicity of grooves which in each case are oriented essentially axially and distributed uniformly over the circumference, wherein in particular a blade is inserted in each groove in each case and positionally fixed there. In an alternative to this, a circumferential groove is introduced into the rotor of the turbine rotor assembly or compressor rotor assembly, wherein a multiplicity of blades are accommodated in an abutting manner in this groove, and are fixed there.

BRIEF DESCRIPTION OF THE DRAWINGS

Two exemplary embodiments of the invention are subsequently explained in more detail with reference to a drawing. In the drawing:

FIG. 1 shows in a cross section a first embodiment of a turbine rotor assembly with a turbine blade comprising a blade airfoil and a blade root,

FIG. 2 shows in a schematic exploded view the blade root according to the first embodiment, and

FIG. 3 shows in a view according to FIG. 2 the blade root according to a second embodiment.

Parts and values corresponding to each other are always provided with the same designations in all the figures.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a turbine rotor assembly 1 in a slightly schematized sectional view. The turbine rotor assembly 1 comprises a rotor 2 consisting of high-grade steel, into which a multiplicity of axial grooves 3 are introduced in a uniform distribution over the circumference. In FIG. 1, only a detail of the rotor 2 in the region of a single axial groove 3 is shown. In the first embodiment which is shown here, each axial groove 3 is essentially constructed as a so-called dovetail groove.

A turbine blade 4 is accommodated in the axial groove 3. The turbine blade 4 comprises a blade airfoil 5 (only partially shown here), and a blade root 6 which serves for anchoring the turbine blade 4 in the axial groove 3.

The blade airfoil 5 is produced from a plurality of layered webs 7 consisting predominantly of unidirectional CFK laminated fabric. The webs 7 in this case are folded in such a way—preferably approximately in the middle—that in the region of the fold 8, which results during folding, a retaining loop 9 is formed. On the side beyond this retaining loop 9 (at the top in the figure), the web ends 10 lie flat upon each other, wherein they are “amalgamated”, giving shape to a blade surface 11 of the blade airfoil 5. The blade surface 11 projects approximately radially from the axial groove 3 of the rotor 2.

A main fiber direction of the CFK laminated fabric is oriented approximately along the webs 7 so that each carbon fiber 12 of the CFK laminated fabric is oriented essentially parallel to the longitudinal sectional surface of the blade airfoil 5 (essentially also forming a loop in each case).

On its outer surface 13, shown here in the manufactured state, the blade airfoil 5 is covered with an erosion-proof coating 14. Alternatively to this, the erosion-proof coating 14 is provided only in the region of the blade surface 11.

The blade root 6 on the one hand comprises an elongated metal core 20 as a carrier which for the attachment of the blade airfoil 5 lies in the retaining loop 9 thereof. The construction of the blade root 6 is explained more accurately based on a three-dimensional exploded view of this in FIG. 2. It becomes apparent from this that the metal core 20 is formed by a round rod consisting of high-grade steel. The surface 21 of the metal core 20 can be provided with a sliding surface 22, consisting of PTFE, for example. At its two ends 23, 24, the metal core 20 is connected to a holder 25 in each case. The two holders 25 are formed essentially by means of congruent, isosceles, trapezoidal steel plates which, corresponding to the dovetail-shaped axial groove 3, can be inserted into this.

Each holder 25, approximately at its surface middle point, has a circular penetration 26 into which the metal core 20 is inserted in an essentially accurately fitting manner, wherein the holders 25 project over the metal core 20 approximately at right angles thereto.

On the two sides 27 of each holder 25, an edge-side recess 28 is introduced into this in each case. These recesses 28 serve for the fixing of two flank sections 30 to which the two holders 25 are connected at the sides 27 in each case in the assembled state.

Each flank section 30 is formed essentially by means of a rectangular, elongated steel plate. Each flank section 30, on its lateral surface 31, has a protrusion 32 which extends in each case over the entire length of the corresponding flank section 30. The protrusions 32 in this case are formed out in each case complementarily to the recesses 28 so that the flank sections 30 can be positionally fixed by the protrusions 32 in the recesses 28.

Each flank section 30 also has a slightly angled edge 33 on the long side. In this case, each flank section 30 is dimensioned in such a way that the straight part of the lateral surface 31 has a width b which corresponds approximately to the side length L of the holders 25. In the assembled state, the flank sections 30 are attached—preferably welded—at both ends to two sides 27 of the two holders 25 in each case. By a lateral edge 34, lying opposite the edge 33, in each case, the flank sections 30 are arranged approximately flush with the long side 35 of the trapezoid, wherein the angled edge 33 projects in each case over the sides 27 on the short side 36 of the trapezoid.

It becomes apparent from FIG. 1 that the projecting edges 33 serve essentially for supporting the blade airfoil 5 in the tangential direction in the assembled state.

It also becomes apparent from FIG. 1 that an average width B (FIG. 2) of each of the holders 25 is dimensioned large enough for this holder to project over the blade airfoil 5 on both sides, that is to say particularly also over the laminated fabric webs 7 in each case, essentially at right angles to the blade surface 14 in the region of the metal core 20 or of the retaining loop 9.

As a result of this, there is no contact between the flank sections 30 and the CFK laminated fabric webs 7 particularly radially at the level of the metal core 20 or of the retaining loop 9. Therefore, even under the influence of a centrifugal force F which occurs during operation of the turbine rotor assembly 1 (acting radially to the rotor), no pressure loading, which is disadvantageous to the CFK laminated fabric, occurs in this region.

During operation, the blade airfoil 5 is therefore aligned along the centrifugal force F direction, as a result of which the blade airfoil 5 is almost exclusively under tensile load, to which the CFK laminated fabric, especially also on account of the favorable main fiber direction, is particularly resistant.

In the embodiment shown here, the two flank sections 30 are welded to the rotor 2 in the axial groove 3.

Shown in FIG. 3 is the blade root 6 according to a second embodiment of the turbine rotor assembly 1 or of the turbine blade 4. The second embodiment corresponds essentially to the first embodiment. In contrast to this, the blade root 6 in this case, for a more favorable load transfer, has a third holder 25 which is arranged approximately in the middle in the longitudinal direction of the metal core 20. This middle holder 25 is constructed similarly to the holders 25 at the ends, wherein the metal core 20 is inserted through the penetration 26.

The blade airfoil 5 is formed in this case by means of two-part webs 7. In the region of the retaining loops 9, the webs 7 are arranged in each case between the holders 25 in the longitudinal direction of the metal core 20, wherein they additionally serve for attachment of the blade airfoil 5 and also for the axial fixing of the middle holder 25.

An embodiment with four or more holders 25 is also conceivable. 

1-15. (canceled)
 16. A blade for a turbine or a compressor, comprising: a blade airfoil; and a blade root, wherein the blade airfoil is produced essentially from a folded laminated fabric web consisting of a fiber-reinforced plastic, in which a retaining loop is formed in a region of the fold, and in which a blade surface is formed from the overlapping web ends, wherein the blade root comprises an elongated carrier and at least two holders connected to the elongated carrier in each case in a positionally fixed manner for anchoring the blade in a corresponding groove of a turbine rotor assembly, and wherein the blade airfoil is attached on the carrier by means of the retaining loop, wherein the individual holders are interconnected by means of a flank section for stabilization, and wherein the flank section is oriented essentially parallel to the carrier.
 17. The blade as claimed in claim 16, wherein each of the holders, in a region of the carrier, at least essentially transversely to the longitudinal extent of the blade airfoil, projects over the carrier on both sides.
 18. The blade as claimed in claim 16, further comprising a third holder for anchoring in a corresponding groove, which third holder is positionally fixed on the carrier at a distance from each of the two holders, which are especially attached at the ends, in the longitudinal direction of the carrier.
 19. The blade as claimed in claim 16, wherein the flank section is connected to the holders in a form-fitting or materially bonding manner.
 20. The blade as claimed in claim 16, the blade including two flank sections which are attached in each case on the lateral edges of the holders which project over the blade airfoil.
 21. The blade as claimed in claim 16, wherein the carrier is round or essentially triangular in cross section.
 22. The blade as claimed in claim 16, wherein the carrier is produced from metal.
 23. The blade as claimed in claim 16, wherein the carrier is provided with a sliding layer on its surface.
 24. The blade as claimed in claim 16, wherein the laminated fabric web is of an essentially unidirectional form, and wherein the main fiber direction of the laminated fabric is aligned as far as possible along an operation-induced centrifugal force direction.
 25. The blade as claimed in claim 16, wherein the blade airfoil is provided at least partially with an erosion-proof coating on its surface.
 26. The blade as claimed in claim 16, wherein the fiber-reinforced plastic is formed as carbon fiber-reinforced plastic.
 27. A rotor assembly, comprising: a rotor, into which a groove is introduced, and a blade as claimed in claim 16, wherein the blade root of the blade lies in the groove, and wherein the blade root, connected to the rotor, is positionally fixed in the groove.
 28. The rotor assembly as claimed in claim 27, wherein the holders and the flank sections are supported on the lateral surfaces of the groove.
 29. The rotor assembly as claimed in claim 27, wherein the holders or the flank sections are supported on the lateral surfaces of the groove.
 30. The rotor assembly as claimed in claim 27, wherein the holders essentially fill out the groove cross section.
 31. The rotor assembly as claimed in claim 27, wherein both the groove and the holders are essentially of trapezoidal design. 